Method for reducing 3-D migration operator to 2-D migration operator for inhomogeneous media

Abstract

Time slices of seismic data are transformed from rectangular space-time domain to cylindrical space-time domain. 2-D seismic migration is performed on the transformed data for each radial direction. Slices of the migrated data are inverse transformed back to the rectangular space-time domain, generated migrated 3-D data for generally inhomogeneous media.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS[0001]Not ApplicableFEDERALLY SPONSORED RESEARCH OR DEVELOPMENT[0002]Not ApplicableSEQUENCE LISTING, TABLE, OR COMPUTER LISTING[0003]Not ApplicableBACKGROUND OF THE INVENTION[0004]1. Field of the Invention[0005]This invention relates generally to the field of geophysical prospecting. More particularly, the invention relates to the field of seismic data processing. Specifically, the invention is a method for imaging the earth through seismic migration.[0006]2. Description of the Related Art[0007]In the oil and gas industry, geophysical prospecting is commonly used to aid in the search for and evaluation of subterranean formations. Geophysical prospecting techniques yield knowledge of the subsurface structure of the earth, which is useful for finding and extracting valuable mineral resources, particularly hydrocarbon deposits such as oil and natural gas. A well-known technique of geophysical prospecting is a seismic survey. In a land-based seism...

AI Technical Summary

Benefits of technology

The invention is a way to turn seismic data into 3D using a method called 3-D seismic migration. This can be useful for analyzing the structure of underground formations. The method involves transforming the data from a rectangular space-time domain to a cylindrical space-time domain and then performing 2D seismic migration on each section of the data. The results are then inverse transformed back to the rectangular space-time domain to create the final 3D data. This technique can be useful for studying the structure of underground formations.

Problems solved by technology

Such seismic reflectors typically are interfaces between subterranean formations having different elastic properties, specifically sound wave velocity and rock density, which lead to differences in acoustic impedance at the interfaces.

Drilling wells to determine whether petroleum deposits are present or not, is an extremely expensive and time-consuming undertaking.

However, three-dimensional (3-D) migration is computationally more complicated than two-dimensional (2-D) migration, because azimuth effects are involved.

Thus, 3-D migration is more expensive than 2-D migration.

In practice, this complication with azimuths presents many more challenges for inhomogeneous (vertically or laterally varying velocity) media than for homogeneous (constant velocity) media.

Because of the azimuth effects involved in 3-D operators and calculations, 3-D migration can not generally be realized exactly by implementation of 2-D migration algorithms.

So, only limited success has been achieved and only exactly in the constant velocity case, using two-step (or two-pass) migration methods.

(1983) show that their method provides increased efficiency when applied to Kirchhoff summation and finite difference techniques, but is found to be less efficient than conventional one-pass 3-D migration in the frequency-wavenumber domain.

For vertically inhomogeneous media, the correct migration velocity is unavailable for the first 2-D migration step, so migrated positions are inaccurate.

(1983) cannot provide the required depth migration version.

This, too, is computationally more expensive in general.

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